Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.24 (mitogen-activated protein kinase)
 95,810 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In the present study, we investigated the cellular mechanism by which oocytes and bone morphogenetic proteins (BMPs) govern FSH-induced steroidogenesis using rat primary granulosa cells. BMP-6 and BMP-7 both inhibited FSH- and forskolin (FSK)-induced progesterone synthesis and reduced cAMP synthesis independent of the presence or absence of oocytes. BMP-7 also increased FSH-induced estradiol production, and the response was further augmented in the presence of oocytes. In contrast, BMP-6 had no impact on estradiol synthesis regardless of the presence of oocytes. Because BMP-7 changed neither FSK- nor cAMP-induced estradiol production, the BMP-7 action was mediated through a FSH receptor signaling mechanism that was independent of cAMP-protein kinase A pathway. Treatment with FSH but not cAMP activated ERK1/2 phosphorylation in granulosa cells, which was further accelerated by oocytes. A specific ERK inhibitor, U0126, increased estradiol production and decreased FSH- and FSK-induced progesterone production and cAMP synthesis. This suggests that ERK activation is directly linked to inhibition of estradiol synthesis and amplification of cAMP. Moreover, FSH-induced ERK1/2 phosphorylation was inhibited by BMP-7 but not influenced by BMP-6. In contrast, BMP signaling including Smad1/5/8 phosphorylation and Id-1 transcription was up-regulated by FSH and oocytes in granulosa cells through inhibition of Smad6/7 expression. Collectively, oocytes enhance FSH-induced MAPK activation and BMP signaling in granulosa cells, which leads to differential regulation of steroidogenesis elicited by BMPs in the presence of FSH in developing follicles.
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PMID:Differential regulation of steroidogenesis by bone morphogenetic proteins in granulosa cells: involvement of extracellularly regulated kinase signaling and oocyte actions in follicle-stimulating hormone-induced estrogen production. 1700 91

The objective of this study was to determine the major intracellular signalling pathways used by FSH and insulin to stimulate cytochrome P450 aromatase (Cyp19) mRNA and oestradiol accumulation in oestrogenic bovine granulosa cells in vitro. Bovine granulosa cells from small follicles (2-4 mm diameter) were cultured for 6 days under non-luteinizing conditions in the presence of insulin at 100 ng/ml, or insulin (10 ng/ml) and FSH (1 ng/ml). On day 4 of culture, specific inhibitors of phosphatidylinositol 3-kinase (PI3K; LY-294002), protein kinase C (PKC; GF-109203X), protein kinase A (PKA; H-89) or mitogen-activated protein (MAP) kinase activation (PD-98059) were added. The addition of PI3K and PKC inhibitors, but not of PKA inhibitor, significantly decreased insulin-stimulated Cyp19 mRNA levels and oestradiol accumulation (P < 0.001). The PKA inhibitor significantly decreased FSH-stimulated Cyp19 mRNA abundance and oestradiol secretion, whereas PI3K and PKC inhibitors decreased oestradiol secretion without affecting Cyp19 mRNA accumulation. Inhibition of MAP kinase pathway significantly increased Cyp19 mRNA abundance in insulin- and FSH-stimulated cells. P450scc mRNA levels and progesterone secretion were not affected by any inhibitor in either experiment. Although FSH stimulates Cyp19 expression predominantly through PKA, oestradiol secretion is altered by PI3K and PKC pathways independently of Cyp19 mRNA levels. In addition, we suggest that Cyp19 is under tonic inhibition mediated through a MAP kinase pathway.
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PMID:Control of oestradiol secretion and of cytochrome P450 aromatase messenger ribonucleic acid accumulation by FSH involves different intracellular pathways in oestrogenic bovine granulosa cells in vitro. 1712 51

The asynchronous secretion of gonadotrope LH and FSH under the control of GnRH is crucial for ovarian cyclicity but the underlying mechanism is not fully resolved. Because prostaglandins (PG) are autocrine regulators in many tissues, we determined whether they have this role in gonadotropes. We first demonstrated that GnRH stimulates PG synthesis by induction of cyclooxygenase-2, via the protein kinase C/c-Src/phosphatidylinositol 3'-kinase/MAPK pathway in the LbetaT2 gonadotrope cell line. We then demonstrated that PGF(2alpha) and PGI2, but not PGE2 inhibited GnRH receptor expression by inhibition of phosphoinositide turnover. PGF(2alpha), but not PGI2 or PGE2, reduced GnRH-induction of LHbeta gene expression, but not the alpha-gonadotropin subunit or the FSHbeta subunit genes. The prostanoid receptors EP1, EP2, FP, and IP were expressed in rat gonadotropes. Incubations of rat pituitaries with PGF(2alpha), but not PGI2 or PGE2, inhibited GnRH-induced LH secretion, whereas the cyclooxygenase inhibitor, indomethacin, stimulated GnRH-induced LH secretion. None of these treatments had any effect on GnRH-induced FSH secretion. The findings have thus elaborated a novel GnRH signaling pathway mediated by PGF(2alpha)-FP and PGI2-IP, which acts through an autocrine/paracrine modality to limit autoregulation of the GnRH receptor and differentially inhibit LH and FSH release. These findings provide a mechanism for asynchronous LH and FSH secretions and suggest the use of combination therapies of GnRH and prostanoid analogs to treat infertility, diseases with unbalanced LH and FSH secretion and in hormone-dependent diseases such as prostatic cancer.
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PMID:Reciprocal cross talk between gonadotropin-releasing hormone (GnRH) and prostaglandin receptors regulates GnRH receptor expression and differential gonadotropin secretion. 1713 45

Several studies have suggested that the transcription factor GATA4 plays an important role in ovarian function. This study evaluated the effects of GATA4 on the regulation of the Cyp19 gene in primary rat granulosa cells under basal conditions and in response to stimulation by FSH. A significant increase in GATA4 mRNA, protein, and DNA binding activity was observed in rats treated with pregnant mare serum gonadotropin, a hormone that binds to the FSH receptors, and in granulosa cells incubated with FSH. Enrichment of the Cyp19 promoter was observed in granulosa cells treated with FSH after chromatin precipitation with an anti-GATA4 antibody. Mutation of the GATA binding site on the Cyp19 promoter and inhibition of GATA4 expression with specific small interfering RNA significantly reduced FSH-enhanced Cyp19 expression, whereas overexpression of GATA4 increased Cyp19 promoter activity. A synergistic effect observed between GATA4 overexpression and FSH treatment in Cyp19 expression was abolished by mutating Ser105 in the GATA4 protein or by pretreating granulosa cells with a protein kinase A inhibitor. Inhibition of phosphatidylinositol-dependent kinase (PI3-K)/casein kinase 2 or ERK1/2 attenuated GATA4/FSH synergism, whereas the simultaneous blockade of PI3-K/casein kinase 2 and ERK1/2 activity eliminated Cyp19 stimulation. Finally, we demonstrated that FSH increases GATA4 phosphorylation and that GATA4 activation requires the activation of multiple kinases, including ERK1/2, PI3-K, and protein kinase A. These findings demonstrate that GATA4 contributes in the regulation of Cyp19 expression in the rat ovary and provide the first evidence that FSH regulates GATA4 activity.
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PMID:Follicle-stimulating hormone-induced activation of Gata4 contributes in the up-regulation of Cyp19 expression in rat granulosa cells. 1722 82

Pituitary tumors are a relatively common neoplasia whose pathogenesis is still largely unknown. Recent studies have revealed frequent activating mutations of the gene for B-RAF, an effector of Ras protein in the mitogen-activated protein kinase pathway, in several malignancies, including melanoma, thyroid, colorectal and ovarian cancer. However, analyses of B-RAF mutations in pituitary tumors have not been reported so far. Therefore, in the present study we have investigated the presence of the B-RAF mutations, by polymerase chain reaction (PCR) amplification of the hot spot exons 11 and 15, followed by direct sequencing, in 50 human pituitary adenomas, including 25 NFPA and 25 secreting adenomas (10 GH, 5 PRL, 6 LH and/or FSH, 4 GH/PRL). We found only one V600E mutation in a NFPA sample, suggesting that B-RAF mutations are a rare event in pituitary tumorigenesis.
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PMID:B-RAF mutations are a rare event in pituitary adenomas. 1731 13

Studies in both mammalian and nonmammalian ovarian model systems have demonstrated that activation of the mitogen-activated protein kinase (MAPK) and protein kinase C (PKC) signaling pathways modulates steroid biosynthesis during follicle development, yet the collective evidence for facilitory versus inhibitory roles of these pathways is inconsistent. The present studies in the hen ovary describe the changing role of MAPK and PKC signaling in the regulation of steroidogenic acute regulatory protein (STAR) expression and progesterone production in undifferentiated granulosa cells collected from prehierarchal follicles prior to follicle selection versus differentiated granulosa from preovulatory follicles subsequent to selection. Treatment of undifferentiated granulosa cells with a selective epidermal growth factor receptor (EGFR) and ERBB4 receptor tyrosine kinase inhibitor (AG1478) both augments FSH receptor (Fshr) mRNA expression and initiates progesterone production. Conversely, selective inhibitors of both EGFR/ERBB4 and MAPK activity attenuate steroidogenesis in differentiated granulosa cells subsequent to follicle selection. In addition, inhibition of PKC signaling with GF109203X augments FSH-induced Fshr mRNA plus STAR protein expression and initiates progesterone synthesis in undifferentiated granulosa cells, but inhibits both gonadotropin-induced STAR expression and progesterone production in differentiated granulosa. Granulosa cells from the most recently selected (9- to 12-mm) follicle represent a stage of transition as inhibition of MAPK signaling promotes, while inhibition of PKC signaling blocks gonadotropin-induced progesterone production. Collectively, these data describe stage-of-development-related changes in cell signaling whereby the differentiation-inhibiting actions of MAPK and PKC signaling in prehierarchal follicle granulosa cells undergo a transition at the time of follicle selection to become obligatory for gonadotropin-stimulated progesterone production in differentiated granulosa from preovulatory follicles.
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PMID:Actions of epidermal growth factor receptor/mitogen-activated protein kinase and protein kinase C signaling in granulosa cells from Gallus gallus are dependent upon stage of differentiation. 1740 74

The present study investigated the phosphorylation pattern of mitogen-activated protein kinase (MAPK) in cumulus-oocyte complexes (COCs) during spontaneous and FSH/LH-induced in vitro maturation (IVM). Both isoforms of MAPK were unphosphorylated in oocytes recovered immediately after liberation from follicles and became phosphorylated following 25 h incubation, corresponding to the time of germinal vesicle breakdown (GVBD). In contrast, MAPK was already phosphorylated in minimal amounts in cumulus cells at the time of liberation from follicles and phosphorylation of MAPK increased after 0.5 h incubation. Supplementation of medium with gonadotrophins intensified phosphorylation at 0.5 h incubation, demonstrating the early and rapid action of FSH/LH on MAPK phosphorylation. Phosphorylation of MAPK in cumulus cells peaked after 21 h of incubation, whereas MAPK was almost completely dephosphorylated at the end of incubation (45 h). During subsequent incubation in the absence of added gonadotrophins, between 5 and 10 h exposure to FSH/LH-supplemented medium was required to induce resumption of meiosis in COCs. Phosphorylation of MAPK in oocytes was prevented by the MEK inhibitor U0126, but the inhibitor reduced phosphorylation of MAPK in cumulus cells only during the first 2 h of IVM. The data support the hypothesis that two different MAPK phosphorylation events occurred following gonadotrophin stimulation, one in cumulus cells and the other in oocytes. In cumulus cells, FSH/LH induced early and rapid U0126-insensitive phosphorylation of MAPK, whereas U0126-susceptible MAPK phosphorylation took place in the oocyte itself around the time of GVBD.
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PMID:Mitogen-activated protein kinase phosphorylation patterns in pig oocytes and cumulus cells during gonadotrophin-induced resumption of meiosis in vitro. 1746 6

GnRH applied continuously or in pulses of high frequency increases follistatin, and thereby differentially regulates FSH and LH. This study was conducted in alphaT3-1 and LbetaT2 gonadotroph cells to begin to understand the signaling pathways through which GnRH stimulates follistatin synthesis. GnRH increased follistatin expression and stimulated a follistatin-LUC reporter in LbetaT2 cells, but was inactive in alphaT3-1 cells. GnRH also increased cAMP levels and stimulated a cAMP-responsive promoter only in LbetaT2 cells. Forskolin stimulated follistatin in both cell lines. GnRH activation of follistatin was blocked by the PKA inhibitor H89 and by over-expression of a dominant-negative inhibitor of CREB (A-CREB). Activation was also suppressed by PKC depletion, and was reduced by the PKC inhibitor bisindolylmaleimide. The MEK inhibitor PD98059 blocked activation by GnRH or forskolin implying that MAPK contributes to cAMP/PKA-mediated activation of follistatin. When LbetaT2 cells were transfected with follistatin-LUC together with A-CREB, and perifused with GnRH, activation was blocked during continuous GnRH, but stimulation by hourly GnRH pulses was unaffected. These experiments provide evidence that GnRH stimulates follistatin through multiple signaling pathways, and that cAMP-CREB activation is obligatory when GnRH is applied continuously. The finding that follistatin transcription was CREB-dependent with continuous but not pulsatile GnRH implies that the mode of ligand activation of GnRH receptors modifies the transcriptional response by changing the signaling network. These results provide a mechanism linking GnRH pulsatility to the differential control of FSH-beta and LH-beta gene expression through follistatin.
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PMID:Transcriptional regulation of follistatin expression by GnRH in mouse gonadotroph cell lines: evidence for a role for cAMP signaling. 1748 56

FSH regulates ovarian granulosa cell differentiation not only by activating adenylyl cyclase and protein kinase A (PKA) but also by other complex mechanisms. Using primary rat granulosa cell cultures, we provide novel evidence that FSH rapidly activates two small GTP-binding proteins RAP1 and RAS. FSH activation of RAP1 requires cAMP-mediated activation of exchange factor activated by cAMP/RAPGEF3 whereas FSH activation of RAS and downstream signaling cascades involves multiple factors. Specifically, FSH activation of RAS required Rous sarcoma oncogene (SRC) family tyrosine kinase (SFK) and epidermal growth factor receptor (EGFR) tyrosine kinase activities but not PKA. FSH-induced phosphorylation of ERK1/2 was blocked by dominant-negative RAS as well as by inhibitors of EGFR tyrosine kinase, metalloproteinases involved in growth factor shedding, and SFKs. In contrast, FSH-induced phosphorylation of protein kinase B (PKB/AKT) and the Forkhead transcription factor, FOXO1a occurred by SFK-dependent but RAS-independent mechanisms. The SFKs, c-SRC and FYN, and the SRC-related tyrosine kinase ABL were present and phosphorylated rapidly in response to FSH. Lastly, the EGF-like factor amphiregulin (AREG) activated RAS and ERK1/2 phosphorylation in granulosa cells by mechanisms that were selectively blocked by an EGFR antagonist but not by an SFK antagonist. However, AREG-mediated phosphorylation of PKB and FOXO1a required both EGFR and SFK activation. Moreover, we show that FSH induces AREG and that activation of the EGFR impacts granulosa cell differentiation and the expression of genes characteristic of the luteal cell phenotype. Thus, FSH orchestrates the coordinate activation of three diverse membrane-associated signaling cascades (adenylyl cyclase, RAS, and SFKs) that converge downstream to activate specific kinases (PKA, ERK1/2, and PKB/FOXO1a) that control granulosa cell function and differentiation.
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PMID:Follicle-stimulating hormone induces multiple signaling cascades: evidence that activation of Rous sarcoma oncogene, RAS, and the epidermal growth factor receptor are critical for granulosa cell differentiation. 1753 7

Ets variant gene 5 (ETV5) and glial cell-derived neurotrophic factor (GDNF) are produced in Sertoli cells and required for maintenance and self-renewal of spermatogonial stem cells (SSCs) in mice. Fibroblast growth factors (FGFs) have been reported to stimulate Etv5 mRNA expression, and FSH was shown to stimulate Gdnf mRNA in Sertoli cell cultures, but there is no other information on factors that regulate these key Sertoli cell proteins necessary for stem cell maintenance. In this study, we investigated regulation of ETV5 and GDNF using the TM4 murine Sertoli cell line. FGF2 stimulated a time- and dose-dependent increase in Etv5 mRNA expression, with a maximal 8.3-fold increase at 6 h following 25 ng/ml FGF2 treatment. This FGF2 dose also stimulated Gdnf mRNA at 48 h. FGF2 effects on Etv5 and Gdnf mRNA were partially mediated through mitogen-activated protein kinase (MAPK) and phosphatidyl inositol 3-kinase (PI3K)-signaling cascades. Specific inhibitors of MAPK (PD98059) and PI3K (wortmannin) pathways reduced Etv5 and Gdnf mRNA expression in FGF2-treated cells. Epidermal growth factor (EGF) stimulated Etv5 mRNA but not Gdnf mRNA. TNFalpha and IL-1beta stimulated Gdnf mRNA, but had no effect on Etv5 mRNA. Other hormonal regulators of Sertoli cells such as testosterone, triiodothyronine and activin A did not affect Etv5 or Gdnf mRNA expression. Results with primary Sertoli cell cultures confirmed findings obtained with the TM4 cell line, validating the use of the TM4 model to examine regulation of Etv5 and Gdnf mRNA expression. In conclusion, we have identified common and unique pathways that regulate Etv5 and Gdnf mRNA in Sertoli cells, and FGFs are emerging as key regulators of the Sertoli cell proteins that control SSCs.
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PMID:Common and distinct factors regulate expression of mRNA for ETV5 and GDNF, Sertoli cell proteins essential for spermatogonial stem cell maintenance. 1757 50


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